Cucumber downy mildew is the most important disease in the production of cucumber in the solar greenhouse. If the prevention and control measures are improper, it will easily lead to a reduction in production or even an unacceptable harvest. Since downy mildew occurs quickly and the epidemic is rapid, the use of chemical pesticides for prevention and control is the most important method to control the epidemic. However, how to use pesticides rationally, improve the control effect, reduce the cost of use, and reduce the residual amount of pesticides have become the focus of attention. Combining the cultivation management experience and disease prevention and control experiments in recent years, the author believes that the following four issues should be noted:
First, pay attention to scientific and rational use of drugs, delay drug resistance
1. Avoid single-use drugs for a long time, choose new pesticides for a long time and use only one pesticide, especially the use of a systemic and bactericidal agent with a single control object and a small point of action. The pathogenic bacteria can easily produce drug resistance, and the control effect is reduced. Therefore, we must pay attention to the elimination of old pesticides with poor efficacy and choose to use some new pesticides with high efficacy, low toxicity, and low residue. This will not only reduce the number of drugs used, but also reduce the production cost, but it will also significantly increase the effectiveness of chemical control and slow drug resistance. produce.
2. Protective fungicides and systemic fungicide rotation alternately use good protective bactericides mainly include mancozeb, dasammonium and chlorothalonil. These pesticides have stable efficacy and resistance to drug resistance; Agents are: B-aluminum, metalaxyl, f-fatling, benalaxyl, cymoxanil, Anker, etc. These pesticides are highly effective, but are susceptible to drug resistance. In actual production, it is necessary to rotate reasonably and alternately with various fungicides, which can delay the occurrence of drug resistance and extend the useful life of pesticides.
3. The correct compounding and mixed use of various agents for controlling downy mildew is a combination of systemic fungicide and mancozeb, such as aluminum phosphorus manganese phosphate, metalaxyl manganese zinc, fazulene manganese zinc, cream urea Manganese zinc cyanide; Second, the compound of the systemic fungicide and copper preparations, such as A cupric, Garrinone, f cream Dan and so on. The correct compounding and mixing of pesticides can both expand the scope of pesticides and delay the development of drug resistance.
4. Grasp the appropriate dosage and drug concentration In general, the higher the concentration of the agent, the better the effect of killing pathogens. However, if the application concentration is too high, it will cause excessive drug residues, which will not only produce phytotoxicity, but also increase the resistance of pathogenic bacteria, cause premature pesticide failure, and shorten the useful life of pesticides. Therefore, when using, read carefully the amount of pesticide used in the instructions, and strictly follow the dilution ratio to prepare the liquid.
5. Controlling the frequency of application, mastering the application of reasonable intervals between application times too many, too much, the interval is too short is a major problem in the prevention of cucumber downy mildew. This wastes pesticides, increases production costs, and increases resistance to pathogens. The period of validity of general chemical pesticides is about 7-10d, so the interval between application should be 7-10d.
The frequency of application of cucumber in the solar greenhouse is 2 to 3 times per month, and no more than 4 times.
Second, pay attention to grasping the four key periods of prevention and treatment, so that early prevention
1. The first critical period during the seedling period of cucumber seedlings, due to smaller seedlings, weak resistance, susceptible to bacteria infection, should be sprayed once protective fungicides to ensure that seedlings are not infected by pathogens. When planting, choose disease-free seedlings to plant in the shed.
2. In the second critical period, after the planting and replanting of cucumber, the speed of plant growth accelerated, and downy mildew easily occurred. A protective spraying should be performed to form a protective film around the plants to prevent pathogens from infecting the plants.
3. In the third critical period, after the cucumbers bloomed in the early stage of flowering, the plants were transferred from vegetative growth period to reproductive growth and vegetative growth. The nutrition of the leaves was worse than before. The resistance of the plants was weak, and downy mildew was prone to occur. A fungicide is sprayed in time to prevent the plants from infecting pathogens.
4. In the 4th critical period, during the harvesting period of cucumber harvesting, during the harvesting period of cucumber, most of the nutrients absorbed by the plants were taken away by the fruits and the resistance of the plants was weak; at the same time, the frequency of watering was higher and the humidity in the greenhouse was higher. Invasion of the spores of Downy mildew. Therefore, before the watering, pesticides should be sprayed first to prevent the downy mildew caused by high humidity. At the same time, field investigations should be conducted regularly to find the central diseased plants and immediately use drugs to eliminate downy mildew at the early stage of disease.
Third, pay attention to improve the spraying technology to ensure the quality of medication
1. Spraying should be done so that the spray does not leak, no heavy spray, no leakage, no leakage of trees, spraying must be sprayed from the lower leaves of the guava. Not only the front and back of the plant leaves should be sprayed evenly and thoughtfully, but also the plant base, mulch, greenhouse walkway, greenhouse membrane, gable, and back wall should be sprayed to ensure the quality of spraying and complete sterilization.
2. The spray should catch three key points. First, the greenhouse has high humidity at the front, five plants in the south are prone to disease, and it is necessary to focus on spraying; second, the plants around the central disease strain are susceptible to pathogenic bacteria and should focus on spraying; third, the upper part of the plant. The functional leaves are susceptible to pathogens, and spraying should be emphasized.
3. Determine the spraying time Under normal circumstances, when the light is strong, the temperature is high, and the humidity is high, the photosynthesis, transpiration, and respiration of the cucumber are all strong, and the stomata on the surface of the cucumber stems and leaves are opened, which is favorable for the entry of medicaments; Due to the high humidity, the liquid surface of stems and leaves dries slowly, which is also conducive to the drug being fully absorbed and enhancing the efficacy. However, if the light is too strong and the temperature is too high, it may cause photolysis of the drug or cause phytotoxicity. Therefore, it should not be sprayed before and after noon. In practice, the best application period should be grasped according to the temperature, humidity, and light requirements of the pharmaceuticals to obtain the best control effect. When the temperature is 20-25°C and the relative humidity is 70%--75%, the liquid volatilizes little, most of them are absorbed by the plants, and the bactericidal effect is good. When the temperature is higher than 30°C, the liquid volatilizes quickly, causing the concentration of the leaf agent. Increased, easy to produce harm, the effect is not ideal; when the temperature is lower than 20 °C, relative humidity is higher than 80%, the plant's absorption and utilization of the liquid is less, not suitable for spraying control.
4. One way to improve the use of drugs is to use the smearing method. If there are diseased leaves in rainy weather, 70% mancozeb can be transferred into a paste. The back of the diseased leaf is smeared with a small brush and the second method is smoked, ie in the evening. Disinfection of chlorothalonil aerosols to air sterilize. Third, use dust to use dusters to spray chlorothalonil or antimony dust agents on the leaves of the plants. Spraying time should be selected in the morning or evening.
Fourth, pay attention to combining other methods, do a good job of comprehensive prevention
1. Agricultural disease prevention and selection of disease-resistant varieties, the cultivation of disease-free strong seedlings; the use of balanced formula fertilization technology, supplementation of trace elements, increase carbon dioxide gas fertilizer; drip irrigation or under-membrane submerged irrigation technology to reduce the humidity within the greenhouse to do a good job in the shed, do The disinfection of the tools and walls in the shed will reduce the number of pathogens.
2. The high-temperature sterilization sterilization method is simple, cost-effective and easy to manage. The specific approach is: the temperature meter hung on the top of the cucumber vine, select sunny noon sealed shed, so that the shed temperature rose to 44 - 46 °C, continuous maintenance 2h. During the period of noon dwelling, the temperature was observed every 15 minutes. Below 42°C, the bactericidal effect was not significant. Above 48°C, the plants were easily damaged. After the treatment, the air is released in a timely manner, and the temperature and humidity are eliminated. If the soil is dry, it should be filled with water 1 d before the ditch.
3. Nutritional control The resistance of cucumber plants to downy mildew is related to the soluble sugar content in the plants. In the late growth stage of cucumber, when the sugar content of the juice in the plant is reduced, 100 times of glucose (or sugar) or 200 times of mixture of rice vinegar and urea is sprayed on the leaves; white sugar and urea of ​​1:0.5:100 can also be used. The mixture was mixed with water for 5 times at intervals of 5 days.
4. After lime water was sterilized and sprayed with lime water, the stratum corneum of cucumber stems and leaves was obviously thickened, the bristles became hardened, and the protection performance of the plants themselves was enhanced. Lime water preparation and spraying method: 1kg of lime water is mixed with 14kg of water. After 24 hours or more, 10kg of lime water can be directly applied. The dosage per 1000 square meters is 67.5 kg. Spraying is best done at 4-5 pm on sunny days to prevent evaporation of water, concentrating the solution and burning the leaves. Interval 10 - 15d, continuous spray 2 - 3 times.
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Accuracy
+/-8cm@ 0.1~3.5m
Measuring Unit
cm
Measuring Range (without Reflection)
0.1-12m
Measuring Time
0.1~3 seconds
Measuring Frequency
100 Hz
Laser Class
Class II
Laser Type
650nm, <1mw, red
Weight
About 5g
Voltage
DC2.5V~+3.5V
Serial Level
TTL 3.3V
Size
46*17*7mm
Operating Temperature
0-40 ℃ (32-104 ℉ )
Storage Temperature
-25~60 ℃ (-13~140 ℉)
IT02S Mini Tof Sensor Module Diagram
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